Printing process including physical development of the printing plate image

ABSTRACT

Metal imaged media such as printing plate or printed circuit boards are produced by (a) forming a catalytic nuclei image on a copy medium; (b) uniformly and rapidly wetting the copy medium with a physical developer; (c) subjecting the copy medium and a thin layer of the physical developer to a rocking motion to cause the developer to flow across the image in predominantly laminar flow to provide a substantially uniform source of metal ion from the physical developer over all areas of the surface of the medium to form a metal image in the catalytic nuclei image areas; and (d) washing the developed copy medium to remove substantially all developer from the copy medium. In a preferred process the catalytic nuclei image is formed by exposure of a thin photosensitive layer. Preferably, the final metal image is adherently and intimately bonded to the support and used on a lithographic printing press to produce multiple copies. The invention also includes the apparatus utilized to carry out these processes.

United States Patent 11 1 Shores 1 May 20, 1975 1 1 PRINTING PROCESS INCLUDING PHYSICAL DEVELOPMENT OF THE PRINTING PLATE IMAGE [75] Inventor: Roger W. Shores, Weymouth, Mass.

[73] Assigncc: Itek Corporation, Lexington, Mass.

[22] Filed: Jan. 2, 1974 [21] Appl. No.: 430,109

[52] U.S. Cl. 101/450; 101/454; 96/33; 96/48 PD; 96/48 R; 96/63; 354/327; 101/466 [51] Int. Cl. B4lm I/00; B04n 1/00; G03c 5/24 [58] Field of Search 96/33, 48 PD, 48 R, 63; 354/327; 101/450, 454

[56] References Cited UNITED STATES PATENTS 766,483 8/1904 Wolfe 96/48 R 2,336,509 12/1943 Smith 354/327 2,394,898 9/1945 Dietert 354/327 3,177,790 4/1965 Turner ct a1... 96/63 3,574,618 4/1971 Cronig 96/48 PD 3,776,696 12/1973 Kato et a1. 96/63 3,807,304 4/1974 Gracia et a1. 101/454 FOREIGN PATENTS OR APPLICATIONS 1,797,142 12/1970 Germany 354/327 Primary ExaminerDavid Klein Attorney, Agent, or Firm-Homer 0. Blair; Robert L. Nathans; W. Gary Goodson [57] ABSTRACT Metal imaged media such as printing plate or printed circuit boards are produced by (a) forming a catalytic nuclei image on a copy medium; (b) uniformly and rapidly wetting the copy medium with a physical developer; (c) subjecting the copy medium and a thin layer of the physical developer to a rocking motion to cause the developer to flow across the image in predominantly laminar flow to provide a substantially uniform source of metal ion from the physical developer over all areas of the surface of the medium to form a metal image in the catalytic nuclei image areas; and (d) washing the developed copy medium to remove substantially all developer from the copy medium. In a preferred process the catalytic nuclei image is formed by exposure of a thin photosensitive layer. Preferably, the final metal image is adherently and intimately bonded to the support and used on a lithographic printing press to produce multiple copies. The invention also includes the apparatus utilized to carry out these processes.

4 Claims, 5 Drawing Figures PRINTING PROCESS INCLUDING PHYSICAL DEVELOPMENT OF THE PRINTING PLATE IMAGE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to physical development processes and apparatus and also to processes and apparatus for printing and producing electrical circuits.

2. Description of the Prior Art Copending U.S. Ser. No. 54,627, filed July 13, 1970, now US. Pat. No. 3,807,304 describes a process of producing metal imaged media by means of physical development processes. One of the problems with this process is the lack of reproducible results. Since one of the main applications for this process is in producing high quality printing plates, it is very essential that high quality images are reproducible and consistent. Furthermore, the images tend to suffer from streaking, overdevelopment, and underdevelopment in different areas of the same plate. Also, there is a great need in the printing industry as well as in the printed circuit industry to automate the physical development processes to eliminate the need for expensive and often undependable manual labor.

SUMMARY OF THE INVENTION The physical development process of this invention overcomes the prior art problems of producing consistent high quality images useful, for example, for lithographic printing plates. Further, the process of this invention enables physical development to be accomplished with large size plates (such as 30 X 40 inches or greater) in a highly automated process which produces high quality metal images in a very short period of time. The process of producing this metal imaged copy medium comprises (1) forming a catalytic nuclei image on a copy medium and which image is capable of causing metal deposition from a physical developer comprising a solution of reducible metal ions; (2) uniformly and rapidly wetting said imaged mediumwith a thin layer of said physical developer; (3) subjecting the imaged plate and the thin layer of physical developer to a rocking motion to cause the physical developer to flow across the catalytic nuclei image in predominantly laminar flow, preferably in a back and forth motion, to provide a substantially uniform source of metal ions in all portions of the catalytic nuclei image areas to form metal images in the catalytic nuclei image areas; and (4) washing the developed copy medium to remove substantially all developer from the copy medium.

A preferred process is one wherein the rocking motion is between about 2 and about 6 of pitch with respect to a single axis and at a rate of between about 2 and about 12 cycles perminute. A preferred process also includes the steps of contacting the surface of the imaged medium with a lithographic printing ink which selectively adheres to the image or non-image areas, and then contacting the inked medium with a receptor sheet for the ink to thereby form a print of the original.

The processors and apparatus of this invention are those suitable for carrying out the above-mentioned processes and especially one comprising:

a. wetting means for uniformly and rapidly wetting a copy mediumwitha thin layer of a physical developer comprising a solution of reducible metal ions and a reducing agent for these ions, said medium comprising:

l. a catalytic nuclei image which is capable of causing metal deposition from said physical developer and said catalytic nuclei image being deposited on 2. a superficially roughened substrate;

b. container means for holding the wetted medium and said physical developer;

c. rocking means for said container means for developing said catalytic nuclei image by causing said thin layer of said physical developer to flow back and forth across said catalytic nuclei image in predominantly laminar flow by applying a rocking motion of between about 2 and about 6 of pitch at a rate of between about 2 and about 8 cycles per minute to the container means containing the wetted medium and said thin layer of said physical developer in order to provide an essentially uniform source of metal ions in all portions of the catalytic nuclei image to thereby form metal images adherently and intimately bonded to the substrate; and

d. end means for imparting turbulent flow to said physical developer sufficient to cause mixing of the metal ions within said physical developer and for changing the direction of movement of said physical developer.

PREFERRED EMBODIMENTS The catalytic nuclei image on the copy medium is an image which is capable of causing metal deposition from a physical developer comprising a solution of metal ions. Physical development according to this invention includes so-called electroless plating processes and electrolytic metal plating processes. Suitable catalytic nuclei are well known in the silver halide diffusion transfer art, in the additive printed circuit art, or in the photographic physical development art. These nuclei include all the metals such as palladium, platinum, or sulfides such as nickel sulfide or graphite. Preferably the catalytic nuclei of this invention are those nuclei generated at least in part by photoexposure of a photosensitive layer comprising a photoconductor such as silver halide, titanium dioxide, or zinc oxide.

The step of uniformly and rapidly wetting the imaged copy medium is performed in such a manner that no tracks or finger prints" are left by a hesitating advance of the physical developer over the copy medium surface. This step is preferably conducted by placing the copy medium comprising the catalytic nuclei image in an inclined flat tray containing physical developer in the end of the tray and then beginning the rocking of the tray so that beginning at the lowered end of the tray, the plate is uniformly and rapidly wet with physical developer.

The thin layer of physical developer utilized in the process and apparatus of this invention is preferably less than about inch in depth when the processor container means is in a horizontal position and the copy medium is lying fiat in the bottom of the container means with the physical developer in the container means. More preferably, however, the physical developer layer is about one-eighth inch in depth when the container means is in this horizontal position.

The processor of this invention in its preferred embodiments contains a storage tank for the physical developer with means for automatically filling the container means with the physical developer and draining the container means to return the physical developer to the storage means or to remove it into a waste drain. The processor of this invention also preferably includes an automatic replenishment system whereby fresh physical developer can be added to the physical developer storage means to maintain a constant source of good quality physical developer.

The rocking motion of this invention is intended to include any motion of the tray so as to cause an essentially laminar flow of the physical developer across the copy medium and also resulting in the impact of the physical developer against the ends or sides of the tray or container means sufficient to cause mixing of the physical developer. Preferably, the rocking motion of this invention is that teeter-totter type of movement of the container means about a single axis which divides the lengthwise plane of the bottom of the container.

vmeans into equal portions and results in the back and forth movement of the physical developer. However, it is also possible to achieve the samemovement of the physical developer in the container means by movement of the container means back and forth in the same plane. ltis also possible to generate the desired flow of physical developer over the catalytic nuclei image by pumping, padding, or the like. For purposes of this invention this type of movement of the tray or other like movements are intended to be included in the term.

rocking motion."

Preferably, the processor of this invention includes means for washing both the back and front sides of the developed copy medium of this invention to thereby remove substantially all of the unused developer from the copy medium. Preferably, this washing means includes automatic washing means such as a spray from the bottom of the container means and a spray bar above the container means and also a non-automatic washing means such as a hose with a sprayer attached which enables the operator to provide an additional final wash step above and beyond the one provided by the apparatus in order to ensure complete removal of the developer in order that the metal stains and the like do not appear on the final imaged plate due to eventual reduction of the metal ion even in areas not containing catalytic nuclei but containing unremoved metal ions from the physical developer.

The catalytic nuclei formed by. photoexposure of a photosensitive layer or by printing orinscribing the support may include one of the following:

.1. the image formed on photoexposure, e.g., the latent silver image in silver halide emulsions or the reversible latent image on a reversibly activatable photoconductor such as titanium dioxide;

2. the irreversible image formed by contacting an exposed photoconductor-bearing medium with a sensitizing metal ion, e.g., a solution of silver ion, which can lead to an invisible irreversible image or a visible metal image;

3. the latent ferrous ion image formed by photoexposure of a ferric salt-sensitized medium and then sensitized with silver ion solution to form a silver image;

4. a conductive image or catalytic nuclei image produced by printing or by writing as taught in commonly owned U.S. Ser. No. 2,440, filed Jan. 12, 1970, now abandoned, e.g., by means of a computer;

5. by physically placing a metallic image adjacent to the support;

8. the silver image produced by the silver salt diffusion transfer process.

The thickness of the photosensitive layer or the image-forming layer, and the insulating layer or subbing layer, where present, will depend upon the nature of the photosensitive material, the nature of the binder, where present, the amount of activating radiation utilized, and other like factors. However, in order to obtain an imaging medium capable of rapid processing, it is preferred that the layer of photosensitive material or of catalytic nuclei be relatively thin, preferably less than about 2 microns and more preferably less than about 1 micron in thickness. Most preferably, the layer thickness is from about 0.01 to about 0.5 micron or so thin that it is unlikely that a completely coherent coat ing exists. However, the thickness of the photosensitive layer and the insulating or subbing layer may vary. For example, in the metal support embodiment the coating may be scraped off except for the portions which are immersed in the roughened surface. The coating thickness may be varied according to the effects desired. However, most preferable is a substrate wherein the coating is less than 1 micron in thickness in order to obtain coherent metal images which are adherently bonded to the support by the rapid processing which is most desired.

The silver halide material preferably used for this invention is dispersed in a binder and contains an excess of halide ions as compared to silver ions. The silver halide may be silver chloride, silver bromide, silver iodide or combinations of these. The crystal size of the silver halide is regulated to obtain the desired photographic speed. A silver halide crystal size of less than about 500 A and more preferably from about 30 to A is especially preferred due to the longer wearing properties of the image, high gamma capabilities, and better adhe sion of the metal image to the support. The preferred silver halide layer is one wherein the silver halide grains are dispersed in a binder such as polyvinyl alcohol or gelatin. Polyvinyl alcohol is an especially preferred binder due to the ability to readily produce a small crystal size silver halide. This emulsion is preferably prepared by a dump method whereby a solution of a halide salt, e.g., an alkali metal chloride, is rapidly added to a solution of a soluble silver salt, e.g., silver nitrate, or vice versa. The reason for the improved image qualities when using the small crystal size silver halide is not known for certain. However, it is theorized that it may be due to the improved ability of the smaller particles to get down into the crevices of the grained support, thereby resulting in a better physical interlocking of the image metal with the grain of the support surface and/or to the larger number of catalytic sites for physical development, thereby resulting in a more coherent form of image metal deposit.

It may be desirable to add sensitizing dyes, gamma regulator such as phenylmercuricacetate and physical developer sensitizers such as sulfur compounds as, for

example, tetramethylthiuramdisulfide to the silver halv the quality of the metal deposit formed when I the metallic support with, for example, a graphite p.en-

cil or may be done by applying-a'germ nuclei layer'preferably in a binder'and coated with a photo-impermeablizable layer, then exposing to impermeabli ze the layer in exposed areas.

The photoconductor orphotocatalyst preferred in this invention are silverfhalide and reversibly activatable photoconductors which'upo'n exposure toactivating radiation remain substantially chemically unchanged.

in a process wherein the photosensitive material is on the metal suppo'rt which will ultimately form the printing plate, the insulating layer of this support is one which will photoconductively insulate the photoconductor or other photosensitive material. A photoconto substantially prevent the passage to the conducting metallic support of electrons from the activated photosensitive material, e.g., a photoconductor, causedby exposure to activating radiation. This insulating layer is preferably a solvent impermeable layer at least 14 A in thickness. A preferred printing surface for wear characteristics is an aluminum support having a barrier oxide layer of at least about 100 A and preferably between 100 to 200 A in thickness. This is preferably pro- 'duced by an'ddization for producing a long run printing plate. It is particularly important that the barrier oxide layer be of sufficient thickness and impermeability to prevent deterioration of the photosensitive layer, e.g., a silver halide emulsion, on prolonged storage of at least about 6 months.

lrradiation'sources which are useful in this invention for producing the initial latent image include any of the usual irradiation means commonly used with the selected photosensitive material. Thus actinic light, X- rays, or gamma rays are effective when photoconductors are used. Beams of electrons and other like particles may also he used in the place of the ordinary forms of electromagnetic radiation for forming an image.

These various activating means are designated by the term activating radiation.

The support 'of the copy medium of this invention may be in'any form such as, for example, sheets, ribbons, rolls, etc. This sheet may be made of plastic,

paper or any suitable metal ortheir alloys, as for example the hydrophilic metals such as chromium, nickel, I lead, stainless steel, magnesium, or aluminum; or the oleophilic metals such as copper or zinc. Aluminum is preferred because of itsdesirable physical and chemical properties, as well as its economy. Aluminum as torily serve asa reproduction carrier can be employed.

. For long run printing plates an alloy such as Type l 100 grained, ductive insulator as'herein defined is one which will act aluminum is used which will resist cracking and will have the strength for these long runs.

The support may be of any suitable thickness. However, a thickness from about 0.006 to 0.025 inches is preferredfor use as printing plates, and preferably'for I long run printing plates, the thickness is from about 0.012 to 0.015 inches.

' The physically roughened suport is a support which has been physically, chemically, or otherwise roughened in order that the metallic images are adherently and intimately bonded to the support. Preferred supports which are suitable for this invention are ones having grained, porous, or matted surfaces. Chemically roughened supports are ones which have been treated by suitable acids or bases, and the like to cause the forma'tion of a grain or tooth similar to that formed in physical roughening processes such as brush graining. Preferred surfaces are those which have been brush chemically grained, electrochemically grained, or grained by blasting with abrasive particles I (sand blasting).

. The physical developers useful in this invention are those image-forming systems such as described in U.S. Pat. No. 3,152,903, in U.S. Pat. No. 3,380,823, and in U.S. Pat. No. 3,390,988, incorporated herein by reference. These image-forming materials include prefera- 'bly an oxidizing agent and areducing agent. Such im-' age-forming materials are also often referred to in the art as electroless plating baths. Electrolytic development such as taught in U.S. Pat. No. 3,152,969 can also be used. The oxidizing agent is generally the imageforming component of the image-forming material. Either organic or inorganic oxidizing agents may be employed as the oxidizing component of the imageforming material. The oxidizing and reducing agent may be combined in a single processing bath, may also be in separate bath, or one or both of these components may be incorporated in the imaging medium prior to exposure. Preferred oxidizing agents comprise the reducible metal ions having at least the oxidizing power of cupric ion and include such metal ions as Ag", Hg, Pb, Au, Au, Pt, Pt, Ni, Sn, Pb, Cu, and Cu.

The reducing agent component of the said imageforming materials are inorganic compounds such as the oxalates, formates, and ethylenediaminetetraacetate complexes of metals having variable valence; and organic compounds such as dihydroxybenzenes, aminophenols, and aminoanilines. Also, polyvinylpyrrolidone, hydrazine, and ascorbic acid may be used as reducing agents in this invention. Suitable specific reducing compounds include hydroquinone or derivatives thereof, oand p aminophenol, pmethylaminophenol sulfate, p-hydroxyphenyl glycine, oand p-phenylenediamine, l-phenyl-3-hyrazolidone,

alkali and alkaline earth metal oxalates and formates.

A preferred physical developer useful in this invention is a stabilized physical developer comprising a solution of metal ions, a reducing agent and an ionic surfactant as a developer stabilizer and especially preferred stabilized developer comprises a soluble silver compound, a ferric compound, a ferrous compound and an ionic surfactant such as taught in aforementioned aformentioned U.S. Pat. No. 3,390,988 and in British Pat. No. 1,063,694, also incorporated herein by reference. This physical developer preferably comprises an aqueous solution of ferrous ion, ferric ions, silver ions, a complexing agent for complexing the ferric ions such as an organic acid, and an ionic surfactant as a stabilizing agent and wherein the AE of the devel oper is such that a printing plate as described in this invention can be produced, preferably in a time period of less than about five minutes. A preferred physical de veloper also comprises a non-ionic surfactant as a stabilizer of cationic surfactants in the developer. A preferred developer is an acid-reacting physical developer comprising a soluble silver compound and containing also a ferrous compound, a ferric compound, and an ionic surface-active compound as a development stabilizer, the concentration of the silver compound being greater than 0.006 mols/liter, and that of the ferrouscompound greater than 0.05 mols/liter, the ferric compound being present in a concentration such that the rate of development and/or the period of life of the developer is or are greater than that of those of a reference developer of the composition:

0.050 mols/liter of ferrous sulphate 0.005 mols/liter of ferric nitrate 0.14 mols/liter of citric acid 0.0% mols/liter of silver nitrate and which contains the same stabilizer in the same amount, the rate of development as well as the period of life each being at least equal to that of this reference developer.

Liquid physical developer systems are preferred for use as image-forming materials because of the excellent results obtained therewith. Any suitable solvent may be utilized. However, aqueous processing baths are preferred. While the pH of the developer is not critical, it has been found that with metal base media the best results are obtained with an acid developer, and especially one having a pH of between about 2 and 5, and

especially with organic acids such as citric, gluconic, I

maleic, and oxalic which are metal complexing agents. A pH of about 2 to 3 is especially preferred. It is believed that the acid functions by dissolving the oxide layer on a metal such as aluminum, therefore improving the adhesion and conductivity of the image to the metallic support.

Additionally, the image-forming materials or physical developers may contain organic acids or alkali metal salts thereof, which can react with metal ions to form complex metal anions. Further, the developers may contain other complexing agents and the like to improve image formation and other properties found to be desirable in this art. v

The physical developers of this invention should be applied for a length of time sufficient to obtain an image adherently and, in metal base media preferably conductively, bound to the grained metallic support in order to produce an imaged plate suitable for use as a printing plate. This time period will vary according to the thickness of the photoconductor layer or thickness of the insulating layer or other separation layers, the length of exposure, nature of the binder or insulator material, ratio of photosensitive material to binder, and like factors known to the art. I

A useful plating bath for amplifying a metallic image which is conductively bonded to a metal support is the one comprising a metal ion and a pickling agent for the metal of the metallic support e.g., a solution of copper ethylenediaminetetraacetic acid (CuEDTA) and sodium EDTA.

The metal image of this invention is preferably a lustrous, coherent metal as opposed to the particulate black or dark metal of most photographic images. Furthermore, these images are adherently bonded to the support. The type of image metal plus the bonding to the support gives the plate the capability of being used as a printing plate. Silver images have been found preferable in producing long run printing plates due to their oleophilic properties.

BRIEF DESCRIPTION OFTHE DRAWINGS FIG. 1 is a perspective view of a rocking tray processor for a copy medium containing a catalytic nuclei image.

FIG. 2 is a sectional view of a rocking tray processor in an inclined position containing physical developer and a copy medium comprising a grained support having a catalytic nuclei image in a photosensitive layer.

FIG. 3 is a perspective view of a preferred rocking tray processor for a copy media comprising a catalytic nuclei image comprising a developer replenishment system and other such features.

FIG. 4 is a perspective view of a fixed tray processor for a copy medium containing a catalytic nuclei image.

FIG. 5 is a perspective view of a printing apparatus showing exposure, development, washing, plate prepa ration, and printing sections.

DETAIL-ED DESCRIPTION OF THE DRAWINGS developed image on the copy medium of this invention.

End means 11, side means 12, and bottom means 13 provide means for containing the physical developer of this invention during the rocking motion. Fulcrum means l4'provides an axis for rocking the tray 10 which is preferably located along an axis dividing the plane of the bottom of the tray into two equal rectangles with the longest side of the tray being substantially perpendicular to such axis.

FIG. 2 shows processing tray 20 comprising end means 26 and bottom means 27 which preferably form a rounded corner at the point of intersection of the end means and bottom means to eliminate too vigorous turbulent flow being imparted to the physical developer during the rocking of the tray. The bottom means 27 and end means 26 may be connected at different angles to also effect the type of turbulent flow imparted to the physical developer. For example, a 90 angle will generally impart more turbulence to the physical developer then when this angle of intersection is greater than 90 such as, for example, l20. The processing tray 20 is rocked on fulcrum 28 to provide the rocking motion.

. The fulcrum 28 is preferably equal distance from the to avoid streaking. The processing tray 20 contains a peg means 21 which provides a barrier to prevent the copy medium 23 comprising a grained support 24 such as one made of grained, anodized aluminum coated with a photosensitive layer 25 such as a silver halide layer which has been exposed imagewise to provide a catalytic nuclei image. To accomplish the step of uniformly and rapidly wetting the copy medium 23 comprising the catalytic nuclei image when utilizing a rocking tray processor such as in FIG. 2, it is essential that the processing tray 20 prior to placing the copy medium 23 in the tray be at an inclined position such that when the copy medium is placed in the tray, preferably against the peg means 21, the physical developer 22 in this end of the tray will cover the end of the copy medium. It is also essential that approximately simultaneously with the end of the copy medium 23 being immersed below the surface of the physical developer that the processing tray begin its rocking cycle so that the physical developer is spread out uniformly and rapidly and without any hesitation over the surface of the copy medium 23. It may be desirable in some instances, such as when the copy medium 23 to be developed is considerably smaller than the bottom of the tray 20, to use a clip means to securely fasten the copy medium to the bottom of the tray 20.

In the preferred embodiment it is essential that the rocking of the tray 20 is mechanically regulated so that each copy medium to be processed will have an identical wetting history from the physical developer during the processing cycle thus resulting in an identical development pattern from plate to plate. The development pattern is preferably imperceptible, but if noticeable at all the pattern should be in the form of a barely noticeable grain or a wave pattern which will be uniform from plate to plate. In, its unacceptable form the development pattern is highly visible in the form of fingerprints or background image patterns having no necessary correlation to the exposure pattern but rather correspond to the pattern of wetting of the developer or movement of the developer across the catalytic nuclei image of the copy medium.

FIG. 3 shows a detailed embodiment of the invention wherein the processor of this invention comprises a processing tray having end means 37, side means 38, and bottom means 39 for containing the physical developer and providing suitable turbulent flow and change of direction of the physical developer as described previously. Fulcrum means 47 as described in previous figures provide a means for imparting rocking motion to the processing tray 30. Physicai developer storage tank 42 preferably containing a stabilized physical developer such as a ferrous/ferric silver ion containing physical developer containing ionic surfactants as stabilizing agents can be pumped into the tray automatically by inlet tube 31 and can be removed automatically from the tray back to the physical developer storage tank 42 through outlet tube 32. Pump means 45 is located with respect to adjustable valves 46 and 40 so that physical developer storage tank 42 can provide physical devel oper directly through inlet tube 41 to inlet tube 31 when valve 46 is opened and valve 40 is closed. However, when valve 46 is closed and valve 40 is open, physical developer storage tank 42 becomes a mixing container fo. the physical developer when the pump means 45 is activated. Replenisher tanks 43 contain fresh physical developer preferably inthree or four components for improved long term storage stability which are connected by tubes 44 to physical developer storage tank 42. In processing a series of plates a certain quantity of fresh physical developer from replenisher tanks 43 is automatically added to the physical developer storage tank 42. The proportion and amount of replenisher can be readily adjusted to maintain essentially uniform concentrations of physical developer in physical developer storage means 42 during the processing of many different copy medium such as ex posed printing plates comprising a thin silver halide layer. Twenty to fifty grained anodized exposed silver halide printing plates having a thin silver. halide layer and a size of approximately thirty inches by forty inches may be processed in this tray using a replenishment system of this invention in connection with the rocking tray processor and the preferred ferrous/ferric silver ion physical developer without showing any noticeable change in image quality. Peg means 34 provide a barrier for the copy medium when placed in the bottom of the tray 30 in order that the openings of the outlet tube 32 or the drain means 33 will not be blocked up. The peg means 34 are also positioned in the preferred rocking tray processor to enable the end of the copy medium to be below the surface of the physical developer when the tray is at its maximum lowered pitch from horizontal. Washing means 35 provides means for washing the backside of the copy medium automatically and washing means 36 provides a washing means preferably in the form of a spray bar for automatically washing the physical developer from the front side of the copy medium. The processor of FIG. 3 may also optionally contain auxiliary handwashing means so that an operator who picks the developed copy medium up after the automatic development and washing cycles would be able to handspray both sides of the copy medium to make sure that any remaining physical developer has been removed.

In a preferred processing sequence a preferred copy medium such as a grained, anodized aluminum plate having an exposed thin silver halide layer on the surface thereof is placed in a processor such as shown in FIG. 3 when the preferred physical developer such as a stabilized physical developer comprising a solution of silver ions, ferrous ions, ferric ions, and ionic surfactants as stabilizing agents is in the lowered end of the tray when the tray is at 21 3 pitch. The exposed plate is mechanically placed in the bottom of the tray so that the end of the plate which is about 30 by 40 inches is immersed in the physical developer. At approximately the moment the end of the copy medium goes below the surface of the physical developer the rocking cycle begins and the lowered 'end of the tray begins to raise allowing the physical developer to uniformly and rapidly cover the exposed printing plate. The physical developer moves to the other end of the tray striking the end means 37 at this end of the traywhen it is in its lowered position. The physical developer strikes this end means with sufficient velocity to generate sufficient turbulent flow to provide mixing of the physical developer. A complete cycle is when the tray has gone through one total movement and returned to its original position. For example, if the end of the tray 30 containing the peg means 34 is in its lowered position, a complete cycle takes this end containing the peg means 34 to a horizontal position, then to a raised position, and then returns it to a horizontal position and finally back to its original lowered position. The printing plate is developed preferably for three minutes while the tray is rocking at the rate of approximately nine cycles per minute. The rate of rocking can be varied depending upon the size of the tray, amount and type of developer in the tray, and like factors to enable the desired agitation mixing and laminer flow to be imparted to the physical developer. Preferably, when the tray is about 42 X 52 inches and the preferred aqueous stabilized physical developer is used, the rocking rate will preferably be between about 2 and about 12 cycles per minute and the maximum pitch will be between about 2 and about 6. The amount of physical developer in the tray when the tray is in its horizontal position is preferably below about At inch of physical developer and preferably below about 3/16 to A inch in depth. It is necessary that sufficient liquid be in the tray to wet the copy medium and not allow the copy medium to dry out during'the rocking cycle thereby causing fingerprints and other development imperfections. At the end of the three minute development cycle, the tray is stopped so that the end of the tray containing the drains is in a lowered position and outlet tube 32 is opened allowing the physical developer to drain into the physical developer storage tray 42. When most of the physical developer has drained from the tank 30, outlet tube 32 is closed and drain means 33 is opened. Clean water is then sprayed into the tray by washing means 35 and 36 and the rocking cycle is began again and continued for about 35 seconds to complete approximately two full cycles of the rocking action. The drain means 33 is opened about five seconds after the washing cycle begins and a waste pump is energized. The wash water and waste physical developer may be carried to a reclamation tank for reclaiming the silver ion in the form of silver metal. At the end of the thirty-five second wash cycle, water will cease to be brought into the tray 30 and the drain means will remain open until all of the water has been removed from the tray 30. After processing preferably the operator picks up the developed copy medium and uses a hand water spray on both sides of the plate is ensure that the washing is complete. The operator then presses a button on the processor to allow the physical developer from the replenisher tanks 43 to be automatically fed into the physical developer storage tank 42.

FIG. 4 shows a straight through processor for developing a copy medium according to the process of this invention. The processor comprises transport means which also may be part of a container means for containing the physical developer or other processing solutions. Inlet means 51 comprises a narrow elongated orfice 57 attached to a broader physical developer container means 59 which in turn may be attached to a source of physical developer for providing a thin uniform sheet of fresh mixed physical developer in substantially uniform laminar flow over the surface of a copy medium moving along the transport means 55 from left to right. When the copy medium 52 has contacted the physical developer for sufficient time to obtain the desired metal image, it passes under wash means 54, preferably in the form of a spray bar which sprays water on the copy medium to remove the excess physical developer. Other additional wash means above and below the copy medium would also preferably be added subsequent to wash means 54 and prior to printing plate preparation means 56 to insure complete removal of physical developer from the copy medium. Printing plate preparation means 56 is for improving the printing characteristics of the copy medium and preferably it applies a mercaptan solution or lacquer solution for increasing the oleophilicity of the metal image and a solution of phosphoric acid and/or gum arabic for increasing the hydrophilicity of the background of the copy medium. This printing plate preparation means 56, of course, is an optional means which would not necessarily be utilized if an imaged copy medium were to be utilized for printed circuits, name plates, or other non-printing plate applications.

FIG. 5 shows a printing apparatus comprising an exposure station 60 comprising an exposure source such as a light source 61 and a transport means 62 for transporting the photosensitive copy medium to the development and wash station 63 comprising developer inlet 64 capable of providing a thin layer of uniform laminar flow of freshly mixed physical developer to the surface of the exposed copy medium moving on the transport means 65. As the copy medium passes under the wash means 66, the physical developer is removed from both sides of the developed copy medium. The transport means 65 then conveys the developed, washed copy medium to station 67 for preparing the printing plate for the printing press by, for example, increasing the oleophilicity of the metal image and increasing the hydrophilicity of the nonimage background area of the copy medium by applying, for example, a solution of mercaptan or a lithographic lacquer to the image areas of the plate and phosphoric acid and gum arabic to the background portions of the plate by applicator means 68. The transport means 69 then conveys a plate to the printing press 70 comprising plate drum 76 on which the printing plate is attached, inking rollers 71, water rollers 72, offset drum 73, preferably comprising a resilient ink attacking blanket, pressure drum 74 to provide pressure against the offset drum 73 to cause the ink to be transferred from the offset drum to the receptor sheet 75.

The rate of agitation whether in the rocking tray mode or in the straight through mode or other mode of this invention is very important. By increasing the rate of agitation so long as the amount of turbulence is not so much as to cause distortions in the developer, the

rate of development is increased. For example, the development time can be cut down from three minutes to one minute by simply increasing the rate of agitation of the physical developer over the surface of the copy medium comprising the catalytic nuclei image.

Also it is very critical that in the initial wetting of the copy medium by the physical developer that there be no pauses of the flow of the developer since fingerprints or pause marks" show up in the final developed copy medium. Hence it is very critical that in the rocking tray mode that there be precise cooridination between placing the copy medium in the tray with an end of the copy medium submerged in the developer and the beginning of the rocking cycle. Likewise in the straight through processor it is very critical that the transport means or other means moves the copy medium at a uniform and rapid rate into the physical developer.

I claim:

1. Printing process comprising:

a. forming a catalytic nuclei image on a copy medium comprising a superficially roughened substrate and which image is capable of causing metal deposition reducible metalions; t r

uniformly and rapidly wetting said imaged copy medium with a thin layer of said physical developer;

' from a p hys ical dev eloper comprising a solution of c. subjecting the imaged plate and the thin layer of physical developer to a rocking motion to cause the physical developer to flow back and forth across the catalytic nuclei image in predominantly lami nar'flow, said rocking'motion being between about '2 and about 6 pitch at a rate of between about 2 it ,and'about 12 cycles per minute to provide a substantially uniform source of metal ions in all portions of the catalytic nuclei image areas to form metal images adher'ently and intimately bonded to the substrate of the copy medium;

d. contacting the surface of the imaged medium with 14 a lithographic printing ink which selectively ad heres to the image or non-image areas; and

e. contacting the inked medium with a receptor sheet for said ink to thereby form a print of the original.

2. Process as in claim 1 wherein the catalytic nuclei image is formed at least in part by exposure of a silver halide layer. 3 v

3. Process as in claim 2 wherein steps (b) and (c) are performed by placing the imaged copy medium in the bottom of a tray containing said physical developer in sufficient' quantities to provide a developer depth above the plate surface of about 4: inch.

4.'Process as in claim 3 wherein said physical developer comprises silver ions, ferrous ions, ferric ions, an organic acid complexing agent for the ferric ions, and

an ionic surfactant as a stabilizing agent. 

1. PRINTING PROCESS COMPRISING: A. FORMING A CATALYTIC NUCLEI IMAGE ON A COPY MEDIUM COMPRISING A SUPERFICIALLY RUGHENED SUBSTRATE AND WHICH IMAGE IS CAPABLE OF CAUSING METAL DEPOSITION FROM A PHYSICAL DEVELOPER COMPRISING A SOLUTION OF REDUCIBLE METAL IONS; B. UNIFORMLY AND RAPIDLY WETTING SAID IMAGED COPY MEDIUM WITH A THIN LAYER OF SAID PHYSICAL DEVELOPER; C. SUBJECTING THE IMAGE PLATE AND THE THIN LAYER OF PHYSICAL DEVELOPER TO A ROCKING MOTION TO CAUSE THE PHYSICAL DEVELOPER TO FLOW BACK AND FORTH ACROSS THE CATALYTIC NUCLEI IMAGE IN PREDEOMIANTLY LAMINAR FLOW, SAID ROCKING MOTION BEING BETWEEN ABOUT 2* AND ABOUT 6* PITCH AT A RATE OF BETWEEN ABOUT 2 AND ABOUT 12 CYCLES PER MINUTE TO PROVIDE A SUBSTANTIALLY UNIFORM SOURCE OF METAL IONS IN ALL PORTIONS ON THE CATALYTIC NUCLEI IMAGE AREAS TO FORM METAL IMAGES ADHERENTLY AND INTIMATELY BONDED TO THE SUBSTRATE OF THE COPY MEDIUM; D. CONTACTING THE SURFACE OF THE IMAGED MEDIUM WITH A LITHOGRAPHIC PRINTING INK WHICH SELECTIVELY ADHERES TO THE IMAGE OR NON-IMAGE AREAS; AND E. CONTACTING THE INKED MEDIUM WITH A RECEPTOR SHEET FOR SAID INK TO THEREBY FORM A PRINT OF THE ORIGINAL. LIPOPHILIC BALANCE OF 15, AND II. DECYLDIETHANOL AMIDE.
 2. Process as in claim 1 wherein the catalytic nuclei image is formed at least in part by exposure of a silver halide layer.
 3. Process as in claim 2 wherein steps (b) and (c) are performed by placing the imaged copy medium in the bottom of a tray containing said physical developer in sufficient quantities to provide a developer depth above the plate surface of about 1/8 inch.
 4. Process as in claim 3 wherein said physical developer comprises silver ions, ferrous ions, ferric ions, an organic acid complexing agent for the ferric ions, and an ionic surfactant as a stabilizing agent. 